Again, I think this could be solved by giving the customer the option. Single box is free, double box we pay the delta in cost.
It is the responsibility of the manufacturer to properly package their product for shipping. I have had some box damage with every Axiom product I have purchased. More than once, it damaged the product and rendered the boxes not safe for re-shipping. When I see the quality packaging of my Revel speakers & JL Audio subs, I know there is a better way. Even if it means charging a bit more to cover the cost, my guess is most would be happy to pay it.